1. Field of Invention
The present invention relates to combination and key operated padlocks and more particularly to such a combination and key operated padlock having a window on its housing and a slidable indicator in the window so as to advise the owner of the lock by a different color that the lock has been opened by a key for, example, inspection.
2. Related Art
Combination and key operated padlocks (i.e., padlocks that can be operated by combination or by key) are not new. For example, U.S. Pat. No. 6,848,283 B1 discloses a combination lock capable of being opened by a key or inhibited the same. The features of the “283” patent are below. A cylinder 40 is adapted to prevent a shackle 20 from turning relative to a body 10 when the lock is in a locked position. In the locked position, inserting a key 91 into a keyhole to turn a staged abutment member 80 will open the lock by unlocking the shackle 20 by engaging a ratchet 82 of the abutment member 80 with a ratchet 45 of the cylinder 40 to move the spring-biased cylinder 40 toward inside of the body 10.
The “283” patent has the advantage of opening a lock by a simple mechanism. However, the spring 70 associated with the cylinder 40 is always compressed. Thus, the spring 70 may suffer fatigue after a predetermined times of use. Further, the owner of the lock cannot visually observer that the lock has been opened by a key from the surface of body 10 after the cylinder 40 has returned to its original position.
Still, U.S. Pat. No. 6,877,345 B1 discloses a combination and key operated padlock with indicator. The “345” patent enables the owner of the lock to visually understand whether the lock has been opened by a key 175 or not by displaying a color “red” or “green” of a resettable indicator through a window on its housing. However, its mechanisms are typically relatively complex in constructions, costly to manufacture, and unreliable in use. Thus, the need for improvement still exists.